Phenotypic screening of transgenic and knockout mice for disorders in hematopoietic cell self renewal, differentiation and function will provide useful insights into the genetic basis of hematopoietic biology and diseases. In addition, because the murine hematopoietic system is relatively easy to isolate, manipulate and characterize, it provides a valuable model system for investigating the role of transgenes and gene knockouts on general biologic processes. These investigators have recently developed a semi-automated high throughput screening technique based on flow cytometry to evaluate the effects of alternative culture conditions on human hematopoietic stem cell self renewal and differentiation. This technique, termed Flow Cytometric High Throughput Screening (F-HTS) can efficiently and accurately characterize critical aspects of hematopoietic biology including cell proliferation, differentiation, self renewal and apoptosis. They propose to modify this technique in order to use it as a high throughput screening technique to characterize hematopoietic features of transgenic and knockout mice. In order to adapt the F-HTS as a screening tool int he murine system, they propose to: (1) more fully automate the F-HTS technique through instrument and software aditions, (2) develop F-HTS staining methods for quantitating murine myeloid, lymphoid and stem cells, as well as for measuring intracellular cytokine production and apoptosis, (3) validate the F-HTS technique in a representative panel of wild type and transgenic mice, and (4) develop a web page to disseminate information regarding the F-HTS technique and the results of ongoing studies. These projects will provide the foundation for using the F- HTS technique for efficiency screening large numbers of mutagenized mice for abnormalities of the hematopoietic system and may be adaptable for use in screening other tissues as well. (End of Abstract.)